1. Field of the Invention
This invention generally relates to positioning mechanisms and more specifically to highly precise positioning stages having limited amount of travel.
2. Description of the Related Art
Mechanisms for positioning an object, in general, are well known. For instance, in the semiconductor industry, various xe2x80x9cstagesxe2x80x9d are used to position a semiconductor wafer during its fabrication process. Stages are also used to support and move an electron source (also referred to as xe2x80x9cfield emitterxe2x80x9d; e.g. Schottky field emitter, thermal field emitter) in an electron beam microcolumn (xe2x80x9cmicrocolumnxe2x80x9d). Microcolumns are physically short electron beam columns that output low-energy electron beams (typically 1-2 keV). Microcolumns are structures based on microfabricated electron xe2x80x9copticalxe2x80x9d components and field emission sources and may be used for lithography. Microcolumns are well known; see, for instance, xe2x80x9cElectron-Beam Microcolumns for Lithography and Related Applicationsxe2x80x9d by T. H. P. Chang, et al., Journal of Vacuum Science Technology Bulletin 14(6), pp. 3774-81, November/December, 1996, incorporated herein by reference.
Friction walkers (also known as xe2x80x9cinertial walkersxe2x80x9d or xe2x80x9cpiezoelectric walkersxe2x80x9d) are well known and have been employed to support and move field emitters in microcolumns. Typically, a friction walker has a base, which supports a field emitter, and several piezoelectric modules that are actuated in a xe2x80x9cwalkingxe2x80x9d pattern to move the base, and thus the field emitter, in a straight line. Two separate stages of friction walkers, one for the X-axis and another for the Y-axis, are used to position the field emitter in an X-Y plane.
A problem with friction walkers is that they are difficult to precisely align to a location. Because a friction walker positions a field emitter using a series of discrete steps and the distance traveled with each step varies, a destination location can be missed if a step towards the destination location is longer or shorter than any of the other steps. It is desirable to have a stage with continuous motion to be able to continuously move and then stop the stage once the destination location is reached.
Another problem with friction walkers and other similar stages in the prior art is that they are bulky and occupy a large volume. For example, two stacked stages (on separate horizontal planes) are typically used to achieve movement in two orthogonal directions. It is desirable to have a compact stage for a variety of reasons including to provide more room for other components in the lithography (or other) system wherein the stage is used. For instance, in a lithography system for creating patterns on masks with moveable field emitters, a compact stage allows more field emitters to be packed in a given area, thereby increasing the system""s throughput.
From the foregoing, a precise and compact positioning stage is highly desirable.
The invention relates to a precise and compact positioning stage for very small (e.g. 100 xcexcm, which is 0.1 mm) amounts of travel. A typical application (not limiting) is in an electron beam lithography system using microcolumns. In one embodiment, the stage includes a block which supports the object (e.g. field emitter) to be positioned. The block defines a channel that allows the block to flex along a first axis. Another channel in the block allows the block to flex along a second axis which is perpendicular to the first axis. Actuators are located in the channels to flex the block and thus position the object supported by the block to a desired location in a horizontal plane defined by the first and second axes. In another embodiment, an array of such independently controlled positioning stages is used to position multiple objects.
This stage typically provides very precise but also typically limited amounts of travel in two orthogonal directions.